Topic 8 - Origins Of Genetic Variation

Question 1

What are the 3 different sources of Genetic Variation?

Answer 1

• Meiosis
• Mutation
• Random Fertilisation

Question 2

What are the 2 main ways Meiosis introduces Genetic Variation?

Answer 2

• Independent (Random) Assortment
• Crossing Over

Question 3

What is Independent Assortment?

Answer 3

• Independent Assortment refers to the random combination of Chromosomes in Gametes (during Meiosis).

Question 4

What stage of Meiosis does Independent Assortment occur?

Answer 4

Metaphase I

Question 5

What are the 3 main types of mutations?

Answer 5

• Point/gene mutatiom
• Chromosomal mutation
• Chromosome mutation

Question 6

How are point/gene mutations caused?

Answer 6

• Point/gene mutations occur when there is a miscopying of one or a small number of nucleotides.

Question 7

What are the 3 types of point/gene mutation?

Answer 7

• Substitutions
• Deletions
• Insertions

Question 8

What is a Substitution? (In terms of mutation)

Answer 8

• Substitution is where one base is substituted (swapped) for another.

Question 9

What is Deletion? (In terms of mutation)

Answer 9

• Deletion is where a base in the sequence is completely lost.

Question 10

What is Insertion? (In terms of mutation)

Answer 10

• Insertion is when an extra base is added in to a sequence.

Question 11

What happens in a Chromosomal mutation?

Answer 11

• A Chromosomal mutation involves changes in the positions of genes within the Chromosome.

Question 12

What happens in a Chromosome mutation?

Answer 12

• In a Chromosome mutation, one of 2 things happen:
• An entire Chromosome is lost during Meiosis
• Or, an entire Chromosome is duplicated in one cell by errors in the process.

Question 13

Explain Random Fertilisation as a source of Genetic Variation?

Answer 13

• In sexual reproduction, A male and female’s gametes fuse to form a new genetic individual.
• The male and female are unrelated, therefore they have different combinations of alleles that are passed on.
• The male alone releases millions of sperm cells which are all genetically different.
• This therefore leads to a completely random and new combination of DNA.

Question 14

What is a Polygenic trait?

Answer 14

• Polygenic traits refers to traits which are determined by several interacting genes.